As a result of recent research, immunological techniques have been applied to the measurement of circulating acid phosphatase. This is mainly because in the measurements of its catalytic activity, serum phosphatases of nonprostatic origin contribute to the results. In addition, the catalytic activity of the enzyme is instable. In the course of the planned research, the usefulness of a novel radioimmunoassay procedure, based on employment of the main acid phosphatase of human prostate and having the highest purity of presently available enzymes, will be established in clinical use. A prospective study will be carried out to establish the usefulness of the method in the early diagnosis of prostatic carcinoma. In patients at various stages of prostatic carcinoma, the merits of the method in the follow-up of the course of the disease and in the evaluation of the effect of the various forms of treatment will be clarified. To optimize the diagnostic use of the method in clinical work, eventual diurnal variation and the effect of prostatic manipulation on its concentrations are investigated. In addition, determination of the enzyme in bone marrow aspirates will be compared with that in peripheral serum. The half-line in blood serum of the main prostatic acid phosphatase will be determined and a characterization of macromolecules, sometimes present in blood serum and interacting with the phosphatase, will be attempted. Our preliminary data suggest that in hyperplastic prostate tissue there is another isoenzyme of acid phosphatase. A radioimmunological method for the quantification of this prostatic acid phosphatase will be finalized. The tissue specificity of the isoenzyme will be clarified. In addition, its possible presence in circulation will be investigated and if present, its diagnostic importance will be settled.